From Apple:
You can disable iCloud Photo Library (and recover iCloud storage) for all devices by going to Settings > iCloud > Storage > Manage Storage > iCloud Photo Library beta, then selecting Disable and Delete. Once disabled, you will have 30 days to download your library to at least one device. You can download your photos and videos to your iOS device by turning on Keep Originals or by selecting the items to download from iCloud.com/photos.

I don't use iCloud Photo Library. I store most of my photos in cloud based apps like Box,Dropbox and OneDrive. iCloud Photo Library takes too much of the iCloud storage space. I only use iCloud to back up what is currently on my phone. I do have a few photo on iCloud Photo Sharing. But not many.